Fluorescent glass composition



May. 14, 1946. J. G. HOOLEY 2,400,147

v FLUORESCENT GLASS COMPOSITION Filed July 17, 1942 Wan-Q4311, Qttnmcp Patented May 14, 1946 UNITED STATE 5 PATE T OFFICE FLUORESCENT GLASS COMPOBIHOE Joseph Gilbert Hooley. Corning, N. Y., assigns: to

Corning Glass Works, Corning, N. Y., a corporation of New York Application July, 1942, Serial No. 451,845 9 Claims. (01. ass-sou) This invention relates to classes which will fluoresce when exposed to ultra-violet Such glasses are useful and desirable as enclosing tubes for luminous discharse devices and particularly for the low pressure mercury arc, the light from which is rich in ultra-violet radiations having a wave length of 254 mu.

watt than priorlamps.

The above and other objects may be accomplished by introducing tin or tin and manganese as iluorescing metals into a glass which consists of P205 and Zn(), the molecular ratio of no: to ZnO being from 0.75 to 1.5, and, ii desired,

additionally containing aluminum phosphate Tin and manganese are known fiuorescing agents and it is known to use them in phos-' phate glasses, as is taught in Patent No. 2,042,425. However, the compositions given in the patent contain no zinc and some of them contain large amounts of alkali metal oxides or boric oxide,

ing within the scope of invention, the fluorescence or light value being expressed in terms of lumens per watt which are produced when the glasses are employed as enclosures for the low' pressure mercury are:

coco:

s uaqa The drawing will further illustrate the invention. 1 1

In the figure there is shown in percent by weight a triaxial diagram which represents a portion of the Ternary System ZnO-AlzOa-PaOs a showing the range 040% 2110, 040% M10 substantial quantities of which I have found to weaken the fluorescence of tin and manganese. The maximum light value or total visible lisht emitted by the glasses oi the patent, when made into a mercury discharge tube is 11.2 which is about 6.2 times that or a tube of the same construction and current input but made of ordinary glass, the latter being 1.8. My new glasses are substantially free from alkali metal oxides and boric oxide and have as much astwice the efficiency of the prior classes.

I have discovered that, in a glass consisting approximately of the equimolecula'r binary composition ZnO-PaOs or any mixture of the binaries ZnO-PzOs and Ami-mos. the fluorescence of tin and manganese is particularly high and the physical properties are generally iavorable for flashing or otherwise coating tubes or other enclosures tor luminous discharse devices.

The following compositions, in percent by weight exclusive oi the fluorescing agent as calculated from the batches, illustrate classes falland 50-100% P205. Line D is drawn. between the points'representing the binary composition AhOa-2P=Os, which is equivalent to approximately,26.4% A120: and 73.8% P205. and binary composition ZnO-PzOs. which is equivalent to ap proximately 36.3% ZnO and 63.7% Plot... All compositions tailin: on line D are mixtures of these two Ibinary compcaitions and may be expressed in molecular prmrtlons as where X. is the moi traction of ZnO-PzOs. 4

Low pressure mercury arc lamps enclosed by envelopes or fluorescent glasses, thebase compo- 85 sitlons, oi which are represented by points on or in the immediate neighborhood oi the line D and which contain tin or tin and manganese, will produce about 40 lumens per watt. For example.

the points designated "Composition 1" and "Composition 2 in the drawing show the relative positions of thewabove described classes and 2 respectively with reference to the D line and lamps made irom these glasses produce 39 lumens and 40 lumens per watt respectively. A- similar lamp enclosed in an ordinary clear non-fluorescent glass. on the contrary, will produce only about three lumens per watt under the same conditions. Thus it will be seen that my new classes are about 13 times as eli'ective as non- 'iiuoresoent glasses and are about twice as eiiective as the fluorescent glasses or the above mentloned patenti The full scope oi zinc aluminum phosphate a glasses, according to my invention, lies between mane-1.5mm) +(1'x) (A1203'2.3P20l) and I X(Zn-0.75P:0s) +(1X) (A130: 115F205) respectively, where K is the mol fraction of the zinc phosphate.

In theglasses thus defined, tin or tin and manganese give a high yield of visible light, as stated above. Tin, which is particularly sensitive to excitation by wave length 254 m fluoresces with a,

bluish white light. Only the near or long wave ultra violet excites manganese to fluorescence and such radiations are substantially absent from the low pressure mercury arc. However, I have found that the combination of manganese with tin in the phosphate glasses of my invention produces more lumens per watt from the mercury arc th tin alone. Moreover, the reddish fluorescence oi the manganese combined with the bluish white fluorescence of the tin produces a very close approximation of noon sunlight. Various compounds of tin and manganese may be used in amounts equivalent approximately to 2% to 12% S210 and up to 2.5% MnO. Inasmuch as I have found that the above described high fluorescent efllciency of my glasses is obtained when the glass is melted reducingly, it is advantageous to use stannous and manganous compounds such as chlorides. carbonaceous materials, such as sugar, starch, charcoal, etc., may be employed as reducing agents.

I have found that the presence of at least 4% exclusive of the fluorescing agent, falls within the limits represented by the expressions X(Zn0-1.5 P205) (1-X) (Alz0s-23Pa0u) x(Zn0-0.'l5 P:0s)+(1-X) (AIM-1.6 P205) where x is the mol fraction of the zinc phosphate, the glass being activated by 2% to 12% of stannous oxide and having a light value of at least 20 lumens per watt.

- 2. A fluorescent glass the composition of which,

' exclusive of the fluorescing agent is represented of alumina is desirable because the binary glasses,

although suitable for some purposes, are not sufflciently stable for all purposes and the stability is improved by the presence of alumina. However, too much alumina causes diflicult melting. Therefore, as the preferred embodiment o! my invention within the broader limits of the system defined in the figure, the following compositions are given as ternary base glasses in terms of weight percentage, the fiuorescing agents being approximately by the expression X (Zn0-Pa05)+(1X) (Al20a-2 P205) where X is the mol fraction of the zinc phosphate, the glass being activated by 2% to 12% of stannous oxide and having'a light value of at least 20 lumens per watt.

3. A fluorescent glass the composition of which, exclusive of the fluorescing agent, falls within the limits represented by the expressions where X is the mol traction of the zinc phosphate, the glass being activated by 2% to 12% of stannous oxide and eflective amounts but not more than 2.5% of manganese oxide, and having a light value of at least 20 lumens per watt.

4. A fluorescent glass the composition of which, exclusive of the fluorescing agent is represented approximately by the expression where X is the moi traction of the zinc phosconsidered as additional in terms of weight percentage of the base glass:

.4 Percent P205 -71 ZnO 20-35 To the above glasses is added SnO in the amount 01' 2%-l2% of the base glass and mo in the amount of 0-2.5% oi the base glass. For modifying the expansion coefllcient and softness of the new glasses,'small amounts of alkali metal oxides and boric oxide may be added without much effect on the fluorescence, but addition of more than 2% or 3% of these oxides decreases the fluorescence of the glass and hence is to be avoided in the practice of my invention.

The glasses of my invention have relatively low -melting points as compared with silicate glasses,

provided the aluminacontent is not too high.

Hence luminous discharge devices of the fluores- 1. A fluorescent glass the composition of which, II

phate, the glass being activated by 2% to 12% oi stannous oxide and effective amounts but not more than 2.5% of manganese oxide, and having a light value of at least 20 lumens per watt.

'5. A fluorescent glass which, exclusive of the fluorescing agent, consists of 20% to 35% ZnO and 60% to 71% P205, the glass being activated with 2% to 12% of stannous oxide, the glass having a light value of at least 20 lumens per watt.

6.'A fluorescent glass which, exclusive of the fluorescing agent, consists of ZnO, P205, and A1203, the ZnO being 20% to 35% and the P205 being 60% to 71%, the glass being activated with 2% to 12% of stannous oxide, the glass having a light value of at least 20 lumens per watt.

7. A fluorescent glass which, exclusive of the fluorescing agent, consists of 20% to 35% ZnO and 60% to 71% P205, the glass being activated with 2% to 12% 01' stannous oxide and eflective amounts but not more than 2.5% oi. manganese oxide, and having a light value 01' at least 20 lumens per watt.

8. A fluorescent glass which, exclusive of the fluorescing agent, consists of ZnO, P205 and A1203, the Zn0 being 20% to 35% and the P205 being 60% to 71%, the glass being activated with 2% to 12% of stannous oxide and eflfective amounts but not more than 2.5% of manganese oxide, and having a light value of at least 20 lumens per watt.

9. A fluorescent glass which, exclusive of the fluorescing agent, consists of a mixture of ZnO-PzOs and Al2O3-2P2Ot, the glass being activated with 2% to 12% of stannous oxide and having a light value 01 about 40 lumens per watt.

JOSEPH GILBERT HOOLEY. 

